diff options
| -rw-r--r-- | src/library/scala/util/Try.scala | 29 | ||||
| -rw-r--r-- | test/junit/scala/util/TryTest.scala | 35 |
2 files changed, 64 insertions, 0 deletions
diff --git a/src/library/scala/util/Try.scala b/src/library/scala/util/Try.scala index 89db57a55e..b0cf122f2a 100644 --- a/src/library/scala/util/Try.scala +++ b/src/library/scala/util/Try.scala @@ -111,6 +111,35 @@ sealed abstract class Try[+T] { */ def filter(p: T => Boolean): Try[T] + /** Creates a non-strict filter, which eventually converts this to a `Failure` + * if the predicate is not satisfied. + * + * Note: unlike filter, withFilter does not create a new Try. + * Instead, it restricts the domain of subsequent + * `map`, `flatMap`, `foreach`, and `withFilter` operations. + * + * As Try is a one-element collection, this may be a bit overkill, + * but it's consistent with withFilter on Option and the other collections. + * + * @param p the predicate used to test elements. + * @return an object of class `WithFilter`, which supports + * `map`, `flatMap`, `foreach`, and `withFilter` operations. + * All these operations apply to those elements of this Try + * which satisfy the predicate `p`. + */ + @inline final def withFilter(p: T => Boolean): WithFilter = new WithFilter(p) + + /** We need a whole WithFilter class to honor the "doesn't create a new + * collection" contract even though it seems unlikely to matter much in a + * collection with max size 1. + */ + class WithFilter(p: T => Boolean) { + def map[U](f: T => U): Try[U] = Try.this filter p map f + def flatMap[U](f: T => Try[U]): Try[U] = Try.this filter p flatMap f + def foreach[U](f: T => U): Unit = Try.this filter p foreach f + def withFilter(q: T => Boolean): WithFilter = new WithFilter(x => p(x) && q(x)) + } + /** * Applies the given function `f` if this is a `Failure`, otherwise returns this if this is a `Success`. * This is like `flatMap` for the exception. diff --git a/test/junit/scala/util/TryTest.scala b/test/junit/scala/util/TryTest.scala new file mode 100644 index 0000000000..03604a8065 --- /dev/null +++ b/test/junit/scala/util/TryTest.scala @@ -0,0 +1,35 @@ +package scala.util + +import org.junit.runner.RunWith +import org.junit.runners.JUnit4 +import org.junit.Test +import org.junit.Assert._ + +/* Test Try's withFilter method, which was added along with the -Xfuture fix for SI-6455 */ +@RunWith(classOf[JUnit4]) +class TryTest { + @Test + def withFilterFail(): Unit = { + val fail = for (x <- util.Try(1) if x > 1) yield x + assert(fail.isFailure) + } + + @Test + def withFilterSuccess(): Unit = { + val success1 = for (x <- util.Try(1) if x >= 1) yield x + assertEquals(success1, util.Success(1)) + } + + @Test + def withFilterFlatMap(): Unit = { + val successFlatMap = for (x <- util.Try(1) if x >= 1; y <- util.Try(2) if x < y) yield x + assertEquals(successFlatMap, util.Success(1)) + } + + @Test + def withFilterForeach(): Unit = { + var ok = false + for (x <- util.Try(1) if x == 1) ok = x == 1 + assert(ok) + } +}
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